1. Field of the Invention
The present invention relates to a transparent drying agent and to an organic electroluminescent device provided with this transparent drying agent.
2. Description of the Related Art
The organic electroluminescent device is a self-emission device provided with a luminous layer. This electroluminescent diode is degraded by moisture and oxygen to produce a non-emitting region called a dark spot.
In conventional organic electroluminescent devices, a transparent counter-substrate (glass cover) is applied to an organic electroluminescent substrate provided with a luminous layer by using an adhesive layer in a nitrogen atmosphere, that is, in an atmosphere free from the open air, to protect the diode from moisture and oxygen. However, it is difficult for such an organic electroluminescent device to shut out the intrusion of moisture in the open air completely to protect the diode.
From this fact, in the bottom-emission organic electroluminescent device in which light is extracted from the organic electroluminescent substrate side provided with a luminous layer, a recess portion is formed on the glass cover stuck to this organic electroluminescent substrate with the adhesive layer being interposed therebetween and a colored drying agent is arranged in this recess portion to trap the intruded moisture.
In the top-emission organic electroluminescent device in which light is extracted from the glass cover, on the other hand, the colored drying agent cannot be disposed on the glass cover unlike the bottom-emission type. Therefore, in Jpn. Pat. Appln. KOKAI Publication No. 2003-144830, there is disclosed a top-emission organic electroluminescent device in which a transparent drying agent constituted of, for example, aluminum alkoxide is disposed on the glass cover. However, when the above organic metal complex absorbs moisture, it produces cracks and is made opaque. Thus, the extraction of light from the glass cover is made difficult in a short time after the start of use.
Also, in Jpn. Pat. Appln. KOKAI Publication No. 2006-59571, there is disclosed an organic electroluminescent panel in which a trapping agent such as trioctyl aluminum is formed on the counter-substrate.